Sir

As pointed out in your News feature “Testing times for BSE”, cases of bovine spongiform encephalopathy (BSE) are being reported in growing numbers across continental Europe1. Not only is the disease having an impact on human health and on countries' economies, but it may also cause a catastrophic decline of some endangered European species of animals.

With about 30 cases of BSE detected in Spain in the past few months, the government has adopted measures aimed at arresting its spread. Since 1 January, a national law obliges farmers to incinerate all dead cows, sheep and goats, regardless of whether they are infected. From 1 March, this law has been extended to pigs, poultry and horses, despite no clear evidence for this latter group being a risk for BSE transmission. These measures are laudable from a prophylactic point of view, but they will deprive other species, some endangered, of food.

In Spain, scavenging birds have coexisted with livestock farmers for centuries2. Spain now has 17,500 pairs of griffon vultures (Gyps fulvus), 1,200 pairs of cinereous vultures (Aegypius monachus), 1,300 pairs of Egyptian vultures (Neophron percnopterus) and 80 pairs of bearded vultures (Gypaetus barbatus), comprising 80–99% of the breeding pairs of vultures in the European Union. Spain also supports 80% of European red kites (Milvus milvus) in winter, and the entire world population — 130 pairs — of Spanish imperial eagles3,4 (Aquila adalberti).

Spanish populations have been used for captive breeding and reintroduction programmes in France, the United Kingdom, Italy, Germany and Austria, where the species are extinct or nearly so. The four species of vulture obtain 60–100% of their food from livestock carrion either abandoned or left out for them5. Griffon vultures alone eat about 10,000 tonnes of dead livestock per year4.

On 22 February, Spanish environmental groups and ecologists working on vulture conservation urged the government to consider measures to protect human health that are compatible with wildlife conservation4. This is not an easy task.

The first priority is that food destined for vultures must be free of BSE to avoid any risk of disease transmission to other species. But, as reported in your News feature, there is no diagnostic test yet available that reliably detects which animals are incubating the disease. Even poultry and pigs are now cautiously considered as at risk, although transmission of BSE to chickens has not proved possible even by direct brain inoculation.

Second, research is needed to design a network of installations to provide food to scavenging birds while excluding other scavengers such as foxes. If their main food source is removed and no remedial action taken, populations will crash and decades of European efforts to conserve endangered birds will have been in vain.